1. Field
The present invention generally relates to ultrasound image processing, and more particularly to an apparatus and method for forming an ultrasound image.
2. Background
An ultrasound system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound system has been extensively used in the medical profession. Modern high-performance ultrasound systems and techniques are commonly used to produce two or three-dimensional diagnostic images of internal features of an object.
Generally, the ultrasound system includes a plurality of transducers for transmitting and receiving a wide band ultrasound signal. When a transducer is stimulated electrically, an ultrasound signal is generated and transferred to the object. The ultrasound signal is reflected from the object, wherein the reflected ultrasound echo signal is transferred to the transducer and converted to an electric signal. The converted electric signal is amplified and signal-processed to generate an ultrasound image data.
In the ultrasound system, a plurality of image frames according to a plurality of viewpoints or angles can be combined spatially to form a composite image. FIG. 1 is a diagram showing the conventional scan lines of a plurality of image frames for forming a composite image. As shown in FIG. 1, the ultrasound signal is transmitted and received in 3 observational directions via a plurality of transducers T1-TN to obtain 3 frames 21-23. The obtained frames 21-23 are then combined spatially to form a composite image 24, as shown in FIG. 2. Specifically, the ultrasound signal is transmitted and received along a reference scan line group SR1-SRN via the transducers T1-TN to obtain a reference frame 21. The ultrasound signal is transmitted and received along a first scan line group SA1-SAN, wherein each scan line is steered to each scan line of the reference scan line group SR1-SRN by a predetermined angle +⊖, via the transducers T1-TN to obtain a first frame 22. The ultrasound signal is transmitted and received along a second scan line group SB1-SBN, wherein each scan line is steered to each scan line of the reference scan line group SR1-SRN by a predetermined angle −⊖, via the transducers T1-TN to obtain a second frame 23. In the ultrasound system, a spatially overlapped area A between the obtained reference frame 21 and the first frame 22, a spatially overlapped area B between the reference frame 21 and the second frame 23, as well as the reference frame 21, are combined to form the composite image 24.
However, the conventional ultrasound system has drawbacks in that the number of image frames necessary for forming a composite image is limited since an odd number of image frames are used to form a composite image.
Moreover, the conventional ultrasound system has a problem of degrading the quality of the composite image, as shown in FIG. 2. That is, the boundary line SAN of the first frame 22 and the boundary line SB1 of the second frame 23 are shown in the composite image 24. This is because the spatially overlapped area A between the reference frame 21 and the first frame 22, the spatially overlapped area B between the reference frame 21 and the second frame 23, as well as the reference frame 21, are combined.